Fireplace Mantels (Building with unusual specs)

I wish to build a mantel for my fireplace and have found the Video provided on Mr. Vila's website helpful. However, our fireplace is a bit unusual in that the entire chimney brick is exposed from floor to ceiling and protrudes out from the wall. I would like to completely cover the brick work by extending the mantel beyond the shelf to meet the ceiling-- resulting in an incased fireplace with only the hearth and surrounding brick showing around the hearth opening. Would I follow the hearth building directions and then add a sort of "hutch" on top of the mantel shelf? Also how should the directions be altered to accommodate nailing/drilling into the masonry instead of a wall?

I would attach to this masonry with polyurethene glue, PL Premium is one good to use here. Attach sleepers first to anil and screw finish surfaces to.

There could eb one problem with this thiough, in not knowing how your chimney was built. A typical chimney should not be in direct contact with combustable materials. That may be why yours is exposed. If there is sufficient masss between the flue and the wood, you are OK, but check with local codes people.